1. Field of the Invention
The present invention relates to a cylinder assembly suitably used, for example, for a work support of a machine tool.
2. Explanation of Related Art
For instance, a conventional work support cylinder assembly comprises only one cylinder for working, as disclosed in Japanese Patent Public Disclosure No. 10-146733 proposed by the present inventors (or U.S. Pat. No. 5,979,267 which corresponds to the Japanese publication).
An example of the cylinder assembly of this kind that the present inventors know comprises two cylinders of a working cylinder and an advancing and retreating cylinder, and it operates as follows.
When performing a locking operation, first, an advancing and retreating piston of the advancing and retreating cylinder ascends to bring a support rod into contact with a workpiece by an urging force of an advancing spring. Thereafter, the working cylinder holds and fixes the support rod at a raised position. Further, when making a releasing operation, first, the support rod is cancelled from the condition held and fixed by the working cylinder. Then the advancing and retreating piston descends, thereby enabling the support rod to move down against the urging force of the advancing spring.
The conventional technique which comprises the two cylinders had a problem that when cancelling the support rod from the held and fixed condition, the support rod protrudes up the workpiece by resorting to the urging force of the advancing spring.
The present invention has an object to provide a cylinder assembly which can solve such a problem as mentioned above.
In order to accomplish the above object, the present invention has constructed a cylinder assembly in the following manner, for example, as shown in FIG. 1, FIGS. 2A to 2F and FIGS. 3A to 3F or in FIGS. 4 to 6.
The cylinder assembly comprises a first working cylinder 20 and an advancing and retreating cylinder 32. The first cylinder 20 performs a locking operation when a gas pressure of an actuation chamber 23 has exceeded a first set pressure (P1) and can make a releasing operation when the gas pressure of the actuation chamber 23 has decreased to a second set pressure (P2) lower than the first set pressure (P1). The second cylinder 32 comprises a second piston 35 fitted into a second cylinder bore 33, an inlet chamber 41 formed between a first end wall 40 of the second cylinder bore 33 and the second piston 35, which pressurized gas is supplied to and discharged from, an outlet chamber 45 formed between a second end wall 44 of the second cylinder bore 33 and the second piston 35, and a return means 46 which retracts the second piston 35 to the first end wall 40. The actuation chamber 23 communicates with the outside air through the outlet chamber 45. A flow resistance applying means (K) is provided in a route between the actuation chamber 23 and the outside air. A changeover means 61 is provided for communicating the actuation chamber 23 with the inlet chamber 41 or the outlet chamber 45. The changeover means 61 communicates the actuation chamber 23 with the outlet chamber 45 during a term from the beginning to the end of an advancing movement of the second piston 35. On the other hand, it communicates the actuation chamber 23 with the inlet chamber 41 at the terminal of the advancing movement of the second piston 35.
The above-mentioned invention operates in the following way, for example, as shown in FIGS. 2A to 2F and in FIGS. 3A to 3F.
When performing the locking operation, pressurized gas such as compressed air is supplied to the inlet chamber 41. Then while the inlet chamber 41 has its pressure (M) increased as indicated by a full line in FIG. 2F, the actuation chamber 23 has its pressure (N) increased in delay from the increase of the pressure (M) of the inlet chamber 41 by an action of the changeover means 61, as shown by a broken line in FIG. 2F. Therefore, first, as shown in FIGS. 2A to 2D, the pressure of the inlet chamber 41 raises the second piston 35 (and an operation member 51 connected to the second piston 35) and then the pressure (N) of the actuation chamber 23 becomes higher than the set pressure (P1), thereby advancing a first piston 22 of the first cylinder 20 to a locking side as shown in FIG. 2E.
Further, when making the releasing operation, the pressurized gas in the inlet chamber 41 is discharged to an exterior area. Then while the pressure (M) of the inlet chamber 41 decreases as indicated by a full line in FIG. 3F, the pressure (N) of the actuation chamber 23 decreases in delay from the decrease of the pressure (M) of the inlet chamber 41 owing to an action of the flow resistance applying means (K), as shown by a broken line in FIG. 3F. Therefore, first, as shown in FIG. 3A to FIG. 3D, the return means 46 lowers the second piston 35 (and the operation member 51) and then the pressure (N) of the actuation chamber 23 becomes lower than the second set pressure (P2), thereby retracting the first piston 22 to a releasing side as shown in FIG. 3E.
In consequence, the present invention offers the following advantage.
When locking, the first cylinder can perform the locking operation after the second piston of the second advancing and retreating cylinder has been advanced. When releasing, the first cylinder can make the releasing operation after the second piston has been retreated.
Accordingly, for example, in the case where the present invention is applied to a work support, at the above releasing time, it is possible to prevent the support rod from protruding up the workpiece by resorting to an advancing means such as the above-mentioned advancing spring.
The present invention includes the following cylinder assembly.
The second cylinder bore 33 has a peripheral surface opened to provide a communication hole 62 which communicates the actuation chamber 23 with an interior area of the second cylinder bore 33. An opening portion of the communication hole 62 and an outer peripheral surface of the second piston 35 constitute the changeover means 61. This invention can form the changeover means 61 into a simple structure with preciseness, which leads to a possibility of putting a reliable cylinder assembly into practice at a low cost.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 4 to 6.
A sealing member 65 is interposed between the peripheral surface of the second cylinder bore 33 and the outer peripheral surface of the second piston 35. This invention enables the sealing member to assuredly prevent the pressurized gas which has been supplied to the inlet chamber from leaking into the outlet chamber. Thus when supplying the pressurized gas, the pressurized gas can be inhibited from leaking from the outlet chamber to the outside air, which results in reducing the consumption amount of the pressurized gas. Besides, it is possible to prevent the leaked pressurized gas from letting constituent members of the cylinder assembly make some misoperation when supplying the pressurized gas.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 4 to 6.
The sealing member 65 is attached to the outer peripheral surface of the second piston 35 and forms one part of the changeover means 61. This invention can provide a changeover means which makes a sure operation and has a simple structure.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 4 to 6.
A restricting passage 66 is provided in the communication hole 62 and forms at least one part of the flow resistance applying means (K). This invention can form the flow resistance applying means into a simple structure with preciseness, which leads to the possibility of putting a reliable cylinder assembly into practice at a low cost.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 4 to 6.
A fitting clearance 67 defined between the peripheral surface of the second cylinder bore 33 and the outer peripheral surface of the second piston 35 forms at least one part of the flow resistance applying means (K). This invention can form the flow resistance applying means into a simple structure with preciseness, which leads to the possibility of putting a reliable cylinder assembly into practice at a low cost.
The present invention includes the following cylinder assembly, for example, as shown in FIG. 1.
The outlet chamber 45 is communicated in series with a rod hole 34 which has a diameter smaller than that of the outlet chamber 45. A piston rod 36 connected to the second piston 35 is inserted into the rod hole 34 with a predetermined annular clearance 37 interposed therebetween. The annular clearance 37 forms at least one part of the flow resistance applying means (K). This invention can form the flow resistance applying means into a simple structure with preciseness, which leads to the possibility of putting a reliable cylinder assembly into practice at a low cost.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 1, 2D and 3B.
There is provided a closing portion 47 which shuts off a communication between the outlet chamber 45 and the outside air at the terminal of an advancing movement of the second piston 35. This invention can surely prevent the pressurized gas which has been supplied to the inlet chamber and the actuation chamber from leaking to the outside air at the terminal of the advancing movement of the second piston.
The present invention includes the following cylinder assembly, for example, as shown in FIGS. 1, 2D and 3B.
The closing portion 47 comprises a valve seat 48 provided on the second end wall 44 of the second cylinder bore 33 and a valve face 49 provided on the second piston 35. This invention can form the closing portion into a simple structure with preciseness, which leads to the possibility of putting a reliable cylinder assembly into practice at a low cost.